Hydrocarbon expulsion model and resource potential evaluation of high-maturity marine source rocks in deep basins:Example from the Ediacaran microbial dolomite in the Sichuan Basin,China

Hydrocarbon expulsion features and resource potential evaluation of source rocks are crucial for the petroleum exploration.High-maturity marine source rocks have not exhibited a hydrocarbon expulsion mode owing to the lack of low-maturity source rocks in deep petroliferous basins.We considered the Ediacaran microbial dolomite in the Sichuan Basin,the largest high-maturity marine gas layer in China,to exhibit a method that quantitatively characterizes the hydrocarbon expulsion of high-maturity marine source rocks.The experiment of fluid inclusion,rock pyrolysis,and vitrinite reflectance(Ro)of 119 microbial dolomite core samples obtained from the Dengying Formation were performed.A hydrocarbon expulsion model of high-maturity source rock was established,and its resource potential was evaluated.The results showed that the Ediacaran microbial dolomite in the Sichuan Basin is a good source rock showing vast resource potential.The hydrocarbon expulsion threshold is determined to be vitrinite reflectance at 0.92%.The hydrocarbon expulsion intensities in the geologic history is high with maximum of 1.6×10^(7)t/km^(2).The Ediacaran microbial dolomite expelled approximately 1.008×10^(12)t of hydrocarbons,and the recoverable resource was 1.5×10^(12)m^(3).The region can be categorized into areasⅠ,Ⅱ,Ⅲ,andⅣ,in decreasing order of hydrocarbon expulsion intensity.Areas with a higher hydrocarbon expulsion intensity have a lower drilling risk and should be prioritized for exploration in the orderⅠ>Ⅱ>Ⅲ>Ⅳ.Two areas,northern and central parts of Ediacaran in the Sichuan Basin,were selected as prospects which had the drilling priority in the future gas exploration.The production data of 55 drilled wells verified the high reliability of this method.This model in this study does not require low-maturity samples and can be used for evaluating high-maturity marine source rocks,which has broad applicability in deep basins worldwide.

Kinetics and model of gas generation of source rocks in the deepwater area, Qiongdongnan Basin

In order to investigate the hydrocarbon generation process and gas potentials of source rocks in deepwater area of the Qiongdongnan Basin, kinetic parameters of gas generation （activation energy distribution and frequency factor） of the Yacheng Formation source rocks （coal and neritic mudstones） was determined by thermal simulation experiments in the closed system and the specific KINETICS Software. The results show that the activation energy （Ea） distribution of C1–C5 generation ranges from 50 to 74 kcal/mol with a frequency factor of 2.4×1015 s–1 for the neritic mudstone and the Ea distribution of C1–C5 generation ranges from 49 to 73 kcal/mol with a frequency factor of 8.92×1013 s–1 for the coal. On the basis of these kinetic parameters and combined with the data of sedimentary burial and paleothermal histories, the gas generation model of the Yacheng Formation source rocks closer to geological condition was worked out, indicating its main gas generation stage at Ro （vitrinite reflectance） of 1.25%–2.8%. Meanwhile, the gas generation process of the source rocks of different structural locations （central part, southern slope and south low uplift） in the Lingshui Sag was simulated. Among them, the gas generation of the Yacheng Formation source rocks in the central part and the southern slope of the sag entered the main gas window at 10 and 5 Ma respectively and the peak gas generation in the southern slope occurred at 3 Ma. The very late peak gas generation and the relatively large gas potential indices （GPI：20×10^8–60×10^8 m^3/km^2） would provide favorable conditions for the accumulation of large natural gas reserves in the deepwater area.

Quick Evaluation of Present-Day Low-Total Organic Carbon Carbonate Source Rocks from Rock-Eval Data: Middle–Upper Ordovician in the Tabei Uplift, Tarim Basin

Previous studies have postulated the contribution of present-day low-total organic carbon （TOC） marine carbonate source rocks to oil accumulations in the Tabei Uplift, Tarim Basin, China. However, not all present-day low-TOC carbonates have generated and expelled hydrocarbons; therefore, to distinguish the source rocks that have already expelled sufficient hydrocarbons from those not expelled hydrocarbons, is crucial in source rock evaluation and resource assessment in the Tabei Uplift. Mass balance can be used to identify modern low-TOC carbonates resulting from hydrocarbon expulsion. However, the process is quite complicated, requiring many parameters and coefficients and thus also a massive data source. In this paper, we provide a quick and cost effective method for identifying carbonate source rock with present-day low TOC, using widely available Rock-Eval data. First, we identify present-day low-TOC carbonate source rocks in typical wells according to the mass balance approach. Second, we build an optimal model to evaluate source rocks from the analysis of the rocks＇ characteristics and their influencing factors, reported as positive or negative values of a dimensionless index of Rock-Eval data （IR）. Positive IR corresponds to those samples which have expelled hydrocarbons. The optimal model optimizes complicated calculations and simulation processes; thus it could be widely applicable and competitive in the evaluation of present-day low TOC carbonates. By applying the model to the Rock-Eval dataset of the Tabei Uplift, we identify present-day iow-TOC carbonate source rocks and primarily evaluate the contribution equivalent of 11.87×10^9 t oil.

Hydrocarbon Generation and Expulsion of the Upper Triassic T3x5Source Rocks in the Western Sichuan Depression: Assessment for Unconventional Natural Gas

Tight-sand gas in the Jurassic and shale gas within the fifth member of Xujiahe Formation （T3xs） in the Western Sichuan Basin （WSD） are currently regarded as the most prolific emerging unconventional gas plays in China. This study conducted a conventional evaluation of T3x5 source rocks in the WSD, and investigated their hydrocarbon generation and expulsion characteristics, including intensity, efficiency and amount. The results show that, the T3x5 source rocks are thick （generally 〉200 m）, and have a high total organic content （TOC）, ranging from 2.5 to 4.5 wt%. It is thus indivative of a great hydrocarbon generation potential when they underwent high thermal evolution （Ro〉1.2%） in the area. In addition, an improved method of hydrocarbon generation potential is applied, indicating that the source rocks reached a hydrocarbon expulsion threshold with vitrinite reflectance （Ro） reaching 1.06%. and that the comprehensive hydrocarbon expulsion efficiency is about 60%. The amount of hydrocarbon generation and expulsion from Tax5 source rocks is 3.14x10^10 t and 1.86x10^10 t, respectively, with a residual amount of 1.28x10^10t within them. Continuous-type tight-sand gas is predicted to have developed in the Jurassic in the Chengdu Sag of the WSD because of the good source-reservoir configuration; the Jurassic sandstone reservoirs are tight, and the gas expelled from the T3xs source rocks migrates for very short distances vertically and horizontally. The amount of gas accumulation in the Jurassic reservoirs derived from T3x5 source rocks is up to 9.3x10s t. Geological resources of shale gas are up to 1.05x10TM t. Small differences between the amounts calculated by the volumetric method and those obtained by hydrocarbon generation potential method may be due to other gas accumulations present within interbedded sands associated with gas shales.

Three-Dimensional Structural Modelling and Source Rock Evaluation of the Quseir Formation in the Komombo Basin,Egypt

The Quseir Formation consists mainly of dark gray mudstones with a high organic matter content and excellent hydrocarbon-generating potential.The main objectives of this study are to highlight the dominant structural elements in the Komombo Basin,Egypt,and evaluate the geochemical characteristics of the Quseir Formation.Depth maps and a 3 D structural model indicate two normal fault trends NW–SE and ENE–WSW.The NW–SE trend is the dominant one that created the primary half-graben system.The depth to the top of the Quseir Formation gradually decreases from the eastern and central parts towards the corners of the basin.The thickness of the Quseir Formation ranges from about 300 to 1000 ft.The 3 D facies model shows that the shale has a large probability distribution in the study area,compared with the sandstone and siltstone.The source rock potential varies between good in the western part to very good in the eastern part of the basin.The organic-rich interval is dominated by gas-prone kerogen type III based on TOC and Rock-Eval.The pyrolysis data vitrinite reflectance(%Ro)(0.5–0.74%)and Tmax values(406–454 C°)suggest a maturity level that ranges from immature to early maturity stage for hydrocarbon generation.

Modeling of the whole hydrocarbon-generating process of sapropelic source rock

Based on experimental data from hydrocarbon generation with a semi-open system, hydrocarbon generation kinetics modeling in gold tube of closed system, high temperature pyrolysis chromatography mass spectrometry experiment with open system and geological data, the characteristics of whole hydrocarbon-generating process, hydrocarbon expulsion efficiency and retained hydrocarbon quantity, origins of natural gas generated in high-over mature stage and cracking temperature of methane homologs were investigated in this study. The sapropelic source rock has a hydrocarbon expulsion efficiency of 30%-60% and 60%-80% in the major oil generation window(with Ro of 0.8%-1.3%) and high maturity stage(with Ro of 1.3%-2.0%) respectively; and the contribution ratio of kerogen degradation gas to oil cracking gas in total generated gas in high maturity stage is about 1:4. The degradation gas of kerogen accounts for 20%, the retained liquid hydrocarbon cracking gas accounts for 13.5%, and the amount of out-reservoir oil cracking gas(including aggregation type and dispersed oil cracking gas) accounts for 66.5%. The lower limit of gas cracking is determined preliminarily. Based on the new understandings, a model of the whole hydrocarbon-generating process of source rock is built.

氦气地质理论认识、资源勘查评价与全产业链一体化评价关键技术

鉴于我国氦气产业链理论技术需求,针对国内外尚无系统的氦气地质理论认识,缺乏针对性的氦气资源评价方法、参数取值标准,缺乏氦气含量综合准确检测、有利富集区优选方法,无成本指标优化体系及全产业链一体化评价方法等卡点和难点,本文运用地质、地球化学、重磁电震、投资经济等多学科方法及实验技术,集中力量攻克氦气成藏机理、资源评价及资产评价的关键技术瓶颈。研发形成1项地质理论认识和3项关键技术:基于典型富氦气藏解剖、地下流体中“氦-气-水”相平衡及相-势耦合分析,研究提出氦气“水溶相、气容相、游离相”3种主要赋存状态、“集流、渗流、扩散”3种运移机理、“近氦源、邻断裂、低压区、高部位”4项分布富集控制因素,初步建立了基于“优质氦源、高效输导、适宜载体”的氦气“生-运-聚”地质理论认识。针对国内氦气含量检测技术参差不齐、部分准确度差、与国外数据差别大、无针对性的氦气资源评价方法等系列难题,以氦气源及氦气含量为核心,研发氦气含量综合准确检测技术,构建4类10种氦气资源评价方法,解决了氦气资源分级分类评价的技术瓶颈。针对基底氦源分布、岩性识别、通源断裂刻画及含氦储层评价难题,创建了归一化重磁下延方案,研发了基于深度学习的多尺度断裂智能识别技术和不同氦气含量下的气藏声学性质模拟方法,为氦源岩分布预测、通源断裂刻画、含氦储层测井解释评价及预测奠定了基础。通过建立多元控氦的富氦区带与目标优选技术,解决了富氦区带与目标优选难题。针对国内贫氦实际情况,以提氦装置投资和操作成本最小化为目标,采用响应面法建立优化目标与各主要工艺参数的非线性回归模型,建立了氦气全产业链一体化评价技术,初步解决了天然气低成本提氦工艺流程优化的技术需求。研究成果为我国长期、安全、规模利用氦气资源资产提供了有效支撑。

长岭断陷SZJ洼槽致密气藏成藏模式及目标优选

为了探寻吉林探区天然气接替资源,本文采用精细智能构造解释技术、低井控下速度场建模技术和特征参数反演技术,对探区内资源潜力最大的松辽盆地长岭断陷SZJ洼槽进行了研究,预测了SZJ洼槽沙河子组烃源岩及储层分布规模和洼槽整体含气性。结果表明:研究区内优质烃源岩生烃叠加面积约356 km^(2),累计厚度100~300 m,沙河子组有利储层分布叠加面积316 km^(2),累计厚度56~125 m。根据分析研究区的源储配置关系,沙河子组致密气藏成藏模式有断鼻式、上倾尖灭式和侧向对接式3种类型;优选出气藏A、B、C 3个高产富集有利目标区。目标区均位于洼槽T 41反射层中部断裂带断背斜圈闭范围内,且优选区已经得到钻井证实。松辽盆地长岭断陷深洼内致密气藏资源潜力较大。

不同类型优质烃源岩生排油气模式

利用地层孔隙异常压力热模拟实验分别对硅质型、钙质型与粘土型优质烃源岩进行分析,生排油气模拟结果表明:(1)成熟早中期硅质型优质烃源岩排油量与排油效率最高,早期主要以重质油排出为主,排油效率高达50%左右;钙质型优质烃源岩次之,排烃效率一般在30%左右;粘土型优质烃源岩排油效率一般只有4%～11%。(2)在成熟中晚期,硅质型优质烃源岩排油效率最高,但是钙质型烃源岩增加迅速达65%,粘土型烃源岩增加不明显。(3)成熟晚期—高成熟阶段,硅质型和钙质型优质烃源岩排油效率变化不明显,而粘土型烃源岩排油效率则从20%迅速增加到90%。硅质型、钙质型和粘土型优质烃源岩生排油气模式之间最大的差异是它们在成熟早中期排油效率和排油量不同。

湖相泥质烃源岩的定量评价方法及其应用

对地层层序、地震相、沉积相、地化分析实验数据以及热演化程度进行了研究,提出了一种定量评价泥质烃源岩的有效方法。在层序地层格架下,以重构声波时差曲线为约束,反演出各沉积相带下的烃源岩分布;采用盆地模拟技术,外推出无实测镜质体反射率(Ro)值井区的Ro数据,经由中子、深侧向电阻率和密度测井曲线获得的成熟度指数的校正后,得出各井的Ro数据,再通过克里金插值生成Ro数据体。烃源岩分布与Ro数据体二者结合即可预测出优质烃源岩的分布。该方法的优点主要表现在将储层预测的随机相控反演运用到有利烃源岩分布的预测中,并将Ro数据由点上升到体,实现了湖相泥质烃源岩的静态定量评价。利用该方法对辽河坳陷西部凹陷清水洼陷的泥质烃源岩进行了评价,取得了较好效果。

排油气门限的基本概念、研究意义与应用

排油气门限是源岩在埋深演化过程中，生油气量饱和了自身吸附、水溶、油溶和毛细管封堵等多种形式的存留需要并开始以游离相大量排出的临界地质条件。研究表明，源岩的排油气门限主要随源岩的有机母质丰度（Ｃ／％）、干酪根类型指数（ＫＴＩ）和转化程度（Ｒｏ／％）三者的不同而改变。应用排烃临界地质条件可以建立源岩概念和差别标准；计算源岩排油气量并确定源岩等级评价标准；研究源岩排油、气相态并分析油气运聚成藏机理；划分源岩排油气阶段并建立源岩排油气地质模式。实际应用表明，用排油气门限、排油气量、排油气阶段、排油气地质模式和排油、气窗等替代生烃研究中的相应概念和术语指导油气田勘探更合理，效果更好。

煤成油地球化学研究现状与展望

重点评述与煤成油理论及勘探实践有密切关系、并在近几年取得重要进展的煤成烃演化模式、煤的生油能力及排油研究3方面的问题。指出：石油地质化学家已更深刻地认识到了煤成烃模式、阶段因地而异的复杂性；建立判别煤系源岩生油能力的标准是煤成油研究中最为重要的进展之一，其中以依据总生烃潜量（S1+S2）、氯仿沥青“A”和总烃含量与有机碳的相关关系建立的判别方案比较实用和有效；比较系统地评述了（与工业性煤成油气聚集有重要关系的）煤成烃排出问题的4种主要研究方法。进展、存在的问题和分歧。在此基础上，展望了对指导煤成油勘探有重要意义的煤系源岩的分布预测、倾油性的进一步判识及排出问题定量研究的发展趋势。

海拉尔盆地断陷比较评价与勘探方向

海拉尔盆地内分布有单断式、双断式和具中央凸起叠合的3类断陷。通过对不同类型断陷比较研究,认为持续沉积的宽深洼槽烃源岩发育,油源充足。砂岩、砾岩、基底变质岩潜山、火山岩均可形成良好储层。有3次生排烃期,原油以侧向和垂向两种方式运移,良好的成藏配置分别构成2～4个生储盖组合、12种油气藏类型。洼槽内部及周缘容易形成各类岩性、构造含油带。已经在贝尔、乌尔逊断陷的主要洼槽内或周边找到4个油田。因此,指出下一步应加强类似查干诺尔、红旗等宽深洼槽的勘探,重视具叠合型和残留型断陷的勘探,注重寻找包括变质岩潜山、断裂坡折带、火山岩等在内的各类油气藏。

地质因素对源岩排烃相态的影响及其贡献评价

用盆地模拟方法综合研究陆相泥质源岩水溶相、扩散相、油溶（气）相和游离相四种形式的综合排烃作用，探讨１３种主要的地质因素对各相态形式相对排烃量的影响及其相对贡献量大小。研究表明，处于不同埋深阶段的陆相泥质源岩排油气相态特征不同，影响因素不同；在一般地质条件下，我国陆相泥质源岩以游离相、油溶相、水溶相和扩散相排出的天然气量分别为４９％、１１％、１８％和２２％左右，以游离相、水溶相和扩散相排出的油量分别为９２％、８％和０％左右。

基于模糊层次分析方法的泥质有效低熟气源岩评价

在特定地质背景下,低熟气可以聚集成藏。由于沉积盆地的古环境、母质类型及有机质演化程度的不同,仅以低熟气源岩物理化学性质为侧重点的烃源岩评价方法很难对不同沉积盆地中的烃源岩的生烃潜力进行相对优劣排序。因此,为了快速有效评价低熟气源岩的生烃潜力,分析了w(TOC)、IH、w("A")等10个因素对气源岩生气能力的影响,建立有效低熟气源岩评价指标体系。并运用层次分析法和模糊数学,建立低熟气源岩生烃潜力评价模型。应用此模型对乌连戈伊气田进行了生烃潜力评价,评价结果表明:Achimov气藏、Bazhenov气藏、Vasyugan气藏、Pokur气藏烃源岩是低熟气源岩;Neocomian气藏和Tyumen气藏烃源岩介于低熟气源岩和常规气源岩之间;Tampey气藏烃源岩属于常规气源岩。这与Galimov所得结论是完全吻合的,说明模型的评价结果是可靠的,可以实现低熟气源岩的综合评价,值得推广应用。

成烃动力学模型在呼和湖凹陷烃源岩评价中的应用

本文利用标定的煤和干酪根成油、直接成气和油成气的化学动力学模型,结合研究区的古热史,对呼和湖凹陷烃源岩的生烃量(史)进行了定量评价。结果表明,成烃的动力学模型不仅可用于烃源岩生烃量(史)的定量计算,而且能为人们深入认识有机质的成烃机理和模式提供有益的启示。

方正断陷有效源岩测井、地震响应及分布预测

方正断陷东部凹陷发育两套烃源岩,底部烃源岩为深灰色泥岩夹薄层煤的煤系地层,顶部烃源岩为半深湖—深湖相的深灰色泥岩,西部凹陷仅发育底部烃源岩,为煤系泥岩。以测井烃源岩评价为基础,采用地震相法在平面上追踪和预测了新安村+乌云组烃源岩的分布范围及厚度。烃源岩测井模拟和地震预测表明:底部有效烃源岩厚度较大,普遍大于40 m,东西凹陷带都有分布;顶部有效烃源岩厚度为30~60 m,主要分布在东部凹陷带的大林子次凹和德善屯次凹。有效烃源岩的分布规律和油气来源研究为油气勘探和石油地质综合研究提供了依据。

地质因素对源岩评价结果的影响及其相对贡献量大小模拟

源岩评价是油气资源评价的基础。目前，基于源岩排烃过程模拟结果可对源岩品质、属性和有效性进行综合定量评价。本文采用盆地模拟技术和不确定性分析方法对影响源岩评价的十三种地质因素的作用大小及其相对贡献量进行评价，同时探讨各种地质因素作用下源岩品质评价指数，属性评价指数和有效性评价指数的变化情况及分布概率。

烃源岩固体有机质测井响应及应用研究

常规录井岩屑的地球化学分析数据连续性差,经常为几米到几十米区间内的统计平均值,指向的地层深度不准确,尤其是海上钻井取心成本高,岩心样品地球化学分析少。为了全面系统评价海上区块烃源岩的空间展布,不漏失单井的薄层烃源岩,在岩心和岩屑样品的实验室岩石物理测量分析基础上,寻找区域内固体有机质的测井响应机理,建立烃源岩评价模型,并利用该模型对文昌A、B凹陷烃源岩层段进行了评价,取得了较好效果。